Flexible double narrowband near-infrared photodetector based on PMMA/core-shell upconversion nanoparticle composites

Flexible narrowband near infrared (NIR) photodetectors (PDs) are urgently in demand in the fastdeveloping era of flexible electronics, due to their crucial roles in various innovative applications. Hence, we designed and synthesized the core-shell structured NaYF4:Yb3+,Er3+@NaYF4:Nd3+ upconversion nanoparticles (UCNPs), which can be pumped by the 808 and 980 nm lights. The upconversion luminescence (UCL) are significantly enhanced after being assembled with the opal photonic crystals (OPCs) due to the photonic crystal effect, with 55 and 48 folds of enhancement factors under illuminations of 808 and 980 nm lights, respectively. Based on this hybrid, the flexible narrowband PDs were successfully fabricated on the PET substrate with the structure of OPCs/NaYF4:Yb3+,Er3+@Nd3+/MAPbI3, which displays excellent detection performance to double narrowband NIR light (808 and 980 nm) benefiting from the amplified UCL, with responsivity of 8.79 and 7.39 A/W, detectivity of 3.01 x 1011 and 2.68 x 1011 cm,Hz1/2/W for 808 and 980 nm lights detection respectively, along with short response time in the range of 120-160 ms. Furthermore, the OPCs/NaYF4:Yb3+,Er3+@NaYF4:Nd3+/MAPbI3 double narrowband PDs display low photodetection power threshold (0.05 W/cm2), outstanding flexibility, prominent moisture resistance, and good long-time stability. This work displays a new concept of narrowband NIR PDs, which open a new field for specific NIR light detections. (c) 2021 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.